By Jonathan Marcus
BBC diplomatic correspondent
The arrest of five Iranian officials, seized by US troops in a raid on an office in Irbil in northern Iraq, could signal a new more assertive US policy towards Tehran.
The US is making its presence felt in the Gulf
Indeed, while President George Bush's speech last week was focused largely on Iraq and the need for a new security plan in Baghdad, one of its notable aspects was its uncompromising tone towards Iran.
Rhetorically, Mr Bush had the Iranian government firmly in his sights. Now there are indications that Washington's tougher words are being matched by a range of practical steps to bring further pressure on Tehran.
Just a few weeks ago, when the bipartisan Iraq Study Group published its report in Washington, one of its central recommendations was that the Bush administration should engage diplomatically with Syria and Iran.
Tehran, so the argument goes, through its close alliance with key Shia factions both inside and outside the Iraqi government, has an important finger in the Iraqi pie.
What could be more logical then than to try to win Tehran over - to seek a deal, hoping, at least, to curtail or constrain Iran's influence?
Pressure on all fronts
President Bush shares this analysis of Iran's role but not the recommended answer of engagement.
Indeed his comments mark a toughening of the US position - a clear sign that Washington now intends to confront Iran's growing influence in Iraq.
"Iran," said the president, "is providing material support for attacks on American troops... We will interrupt the flow of support from Iran and Syria, and we will seek out and destroy the networks providing advanced weaponry and training to our enemies in Iraq."
US forces raided the Iranian liaison office in Irbil
Within hours of the president's speech, US forces raided an Iranian office in Irbil in northern Iraq and detained five staff members.
This undoubtedly signals a ratcheting up of pressure on the Iranians, pressure which is already being applied on a number of other fronts.
Limited economic sanctions against Iran's nuclear programme have been backed by the UN Security Council in New York.
The United States is pressing its closest allies to apply additional sanctions of their own and is leading the way, by - last week, for example - black-listing Iran's fifth-largest bank, alleging that it is involved in financing Iran's missile programmes.
Overt military pressure is also being applied. An additional US aircraft carrier and its accompanying strike group has been deployed to the region.
The message is clear. Both on the nuclear front and in Iraq, Mr Bush seems intent on rolling back Iran's growing influence.
Another straw in the wind is the lively public debate in Israel on the desirability or otherwise of a potential strike on Iran's nuclear sites - perhaps even using tactical nuclear weapons.
Serious strategic analysts question if Israel really has the means to mount the kind of long-range, week-long air campaign that might be needed to significantly damage Iran's nuclear infrastructure.
But the discussion, orchestrated by more hawkish voices, serves a purpose - again it is an effort to step up the pressure on Tehran.
There are rumours about the health of Iran's supreme leader
So can the new US strategy succeed?
There are those who strongly back the toughening US stand against Iranian influence in Iraq.
One leading Sunni politician, Iraq's Vice-President Tariq al-Hashimi, says that Iran has "a deep and exceptional influence" in his country's affairs, something he wants to see much reduced.
But, of course, that is not how many Shia politicians see it, and the detention of the Iranian officials is straining ties between Washington and the Iraqi government at a very inconvenient moment.
So much, then, for Iraq, where the tougher US stand towards Iran looks like creating as many problems as it seeks to resolve.
What about the broader impact on Tehran's regional ambitions?
It is not clear yet how successful the new US approach will be. Bilateral economic sanctions by America's friends could potentially concentrate minds in Tehran, though it is far from clear how many countries are willing to go down this path.
The fluctuating rumours of ill-health surrounding Iran's Supreme Leader Ali Khamenei could also complicate the picture - prompting either a step back from confrontation or more abrasive rhetoric.
Washington's intentions, too, are far from clear. Is Mr Bush seeking to encourage greater pragmatism on the part of the Iranians? Or is this simply the prelude to a more comprehensive attack?
Whether or not the Bush speech represents a new strategy towards Iraq is still a matter of debate. But it decidedly signalled a more muscular US approach towards Iran.